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Isolated Abducens Nerve Avulsion at Pontomedullary Sulcus Following Trivial Head Injury

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Isolated Abducens Nerve Avulsion at Pontomedullary Sulcus Following Trivial Head Injury THIEME Case Report 177 Isolated Abducens Nerve Avulsion at Pontomedullary Sulcus following Trivial Head Injury Sharath Kumar Maila1 Rajani Somappa Sunnadkal2 1 Department of Neurosurgery, Osmania Medical College and Address for correspondence Dr.SharathKumarMaila,MCh, Hospital, Hyderabad, Telangana, India Department of Neurosurgery, Osmania Medical College and Hospital, 2 Department of Radiodiagnosis, Yashoda Superspecialty Hospital, Hyderabad, Telangana 500095, India (e-mail: [email protected]). Somajiguda,Hyderabad,Telangana,India Indian J Neurosurg 2015;4:177–179. Abstract Abducens nerve palsy is commonly seen in neurosurgical practice. However, the abducens nerve palsy secondary to an avulsion injury is extremely rare. The patients Keywords present clinically with diplopia and show lateral rectus palsy. Here, the authors present ► abducens nerve a case report of such an unusual condition following a trivial trauma presenting ► sixth cranial nerve clinically with left lateral rectus palsy. The course of the nerve and a possible palsy mechanism of such an injury and management are discussed. To the authors ► avulsion injury knowledge, there is no reported case of an isolated unilateral avulsion injury of the ► lateral rectus palsy abducens nerve following trauma before this report. Introduction Case History Cranial nerve palsies are debilitating socially and can cause A 31-year-old lady was brought to the emergency disfigurement. Abducens nerve palsy is one of the department of our hospital with a history of slip and fall commonly encountered conditions in the clinical practice. on ground while walking. She complained of double vision The age-adjusted incidence of abducens nerve palsy is 11.3/ with both eyes open since the time of fall. There was no 100,000 in a geographically defined population.1 Head history of loss of consciousness, seizure, vomiting, or ear injury is one of the common causes for the cranial nerve nose throat bleed. On clinical examination she was palsies. The incidence of cranial nerve injury following conscious and responding appropriately to commands closed head injury varies between 5 and 23%.2 The cranial (GCS ¼ E4M6V5). On inspection, she had left esotropia nerves most commonly affected following blunt head (►Fig. 1). trauma are olfactory, facial, and vestibulocochlear Her pupils were equal in size bilaterally and reacting nerves.3 The incidence of unilateral abducens palsy is rare normally to light. She was able to count fingers with each and reported to be 1 to 2.7% of all the head injury cases.4 Of eye individually from a distance of 6 feet. Fundoscopy was the various types of injuries to the abducens nerve normal bilaterally. Examination of extraocular movements unilateral avulsion injury at the pontomedullary junction showed left lateral rectus palsy. Examination of other cranial is extremely rare. Here, we report a case of a 31-year-old nerves, higher central nervous system functions and motor female patient who presented with left lateral rectus palsy and sensory systems were unremarkable. She was due to avulsion injury of the left abducens nerve following hemodynamically stable and no other injuries were a trivial fall. present. She was admitted and initially evaluated with a received DOI http://dx.doi.org/ © 2015 Neurological Surgeons’ Society April 7, 2015 10.1055/s-0035-1569001. of India accepted ISSN 2277-954X. September 22, 2015 published online December 16, 2015 178 Isolated Abducens Nerve Avulsion at Pontomedullary Junction Maila, Sunndakal only the somatic efferent fibers that supply the lateral rectus muscle and helps in the horizontal lateral movement of the globe. Abducens palsy is one of the most commonly encountered false localizing sign secondary to the raised intracranial tension. Abducens nerve dysfunction can occur from lesion anywhere in its course from the pontine nucleus to the lateral rectus muscle in the orbit. The pontine nucleus is present in the Fig. 1 Photograph showing the left esotropia. pons on the floor of the fourth ventricle close to the midline. The axons from the facial nucleus loop around it forming the “facial colliculus” that is evident as noncontrast computed tomography (CT) of brain and small bulge in the floor of the fourth ventricle. The fibers routine biochemical investigations. The CT showed no of the abducens nerve emerge from the brain stem at the evidence of fracture and the normal parenchyma. Her pontomedullary sulcus maintaining the most medial routine biochemistry was unremarkable. Further we position to the exiting facial fibers and entering evaluated her with magnetic resonance imaging (MRI) vestibulocochlear fibers. After exiting from the brain brain including three-dimensional-fast imaging employing stem it has a very long intracranial course traversing the steady-state acquisition (3D-FIESTA) sequence to evaluate prepontine cistern (cisternal segment), cavernous sinus in the left lateral rectus palsy. The MRI showed normal the petroclival region (cavernous segment), and entering neuroparenchyma with no features of hemorrhage or the orbit through the superior orbital fissure (orbital ischemia. 3D-FIESTA sequence acquired showed an abrupt segment). The cisternal segment enters the cavernous discontinuity in the left abducens nerve at the sinus by traversing the Dorello canal. The nerve is mobile pontomedullary sulcus with retracted fibers at petroclival in the subarachnoid space of the prepontine cistern junction (►Figs. 2 and 3). between two relatively fixed points, one at the She was managed symptomatically and was discharged pontomedullary sulcus and the other at the osteofibrous with an advice for regular follow-up and consult ophthalmic compartment at petroclival junction (Dorello canal) and surgeon for further evaluation and management. However, thus making it vulnerable to injury. The proposed her abducens palsy persisted and was complete at 1 month mechanism for the injury in the cases like the present follow-up. case could be a sudden vertical displacement of brain, either downward or upward, causing the stretch of the Discussion nerve fibers between the relatively fixed points, with the apex of the petrous bone acting as the fulcrum, Abducens nerve is one of the important nerves involved thereby causing the avulsion. with the extraocular movements of the globe. It contains Cranial nerves are best imaged with MRI using special sequences like steady-state sequences. These sequences are acquired volumetrically with thin sections and are basically T2-weighted gradient sequences. These sequences are named variously by different vendors as CISS (constructive interference in steady state, Siemens [Erlangen, Germany]), FIESTA (fast imaging employing steady-state precession, [Milwaukee, United States]), and b-FFE (balanced fast field echo, Philips [Eindhoven, the Netherlands]). Axial acquisitions of the brain stem can clearly demonstrate various cranial nerves emerging as dark linear structures on the background of high cerebrospinal fluid signal intensity in the adjacent cisterns. We used 1.5T MRI equipment (GE Medical Imaging, Milwaukee, Wisconsin, United States) with a 3D-FIESTA steady-state sequence for imaging the nerve, which revealed the avulsion in the form of pontine detachment at the pontomedullary sulcus. The prognosis in this type of avulsion injuries is bleak and the deficit is likely to be permanent. Initial management of this condition is symptomatic by occlusion of the eyes with Fig. 2 Axial 3D-FIESTA image showing avulsed left abducens nerve pads and is aimed at prevention of amblyopia in case of (long arrow) in the form of discontinuity at pontomedullary junction. children. The deficit in these cases of total nerve avulsion is cf. Contralateral normal abducens nerve noted in prepontine cistern (short arrow). 3D-FIESTA, three-dimensional-fast imaging employing deemed to be permanent. Surgical intervention may be steady-state acquisition. beneficial in the initial stage of presentation and include Indian Journal of Neurosurgery Vol. 4 No. 3/2015 Isolated Abducens Nerve Avulsion at Pontomedullary Junction Maila, Sunndakal 179 Fig. 3 Coronal 3D-FIESTA image showing nonvisualized cisternal segment of left abducens nerve (short arrow). cf. Normal visualized abducens nerve on the right side (long arrow). muscle transfer procedures like the transfer of vertical recti Presentation at a meeting insertions, or permanent joining of the vertical and lateral None. recti, with or without lateral rectus resection.5 Conclusion Conflict of Interests None. Isolated unilateral abducens nerve avulsion is a rare entity which is not reported till date. Thorough clinical and radiological evaluation is required in such cases. Steady- Acknowledgment state MRI sequence is an excellent modality to pick up the None. cranial nerve injuries in the evaluation of trauma. Once diagnosed an early surgical intervention may be beneficial as the deficit is deemed to be permanent. References 1 Patel SV, Mutyala S, Leske DA, Hodge DO, Holmes JM. Incidence, associations, and evaluation of sixth nerve palsy using a population- based method. Ophthalmology 2004;111(2):369–375 Key Message 2 Kumar N, Mukherjee S, Patel MP, Suni, Abhishek, Bhangale D. Avulsion injury of the abducens nerve following a trivial fall Delayed manifestation of unilateral 6th and 7th cranial nerve palsies following head injury. Indian J Basic Applied Med Res is extremely rare. This injury presents clinically with 2013;2(8):1035–1037 diplopia and manifests as lateral rectus palsy. Early 3 Sam B, Ozveren MF, Akdemir I, et al. The mechanism of injury of surgical correction of esotropia may be beneficial as the the abducens nerve in severe head trauma: a postmortem study. deficit is deemed permanent. Forensic Sci Int 2004;140(1):25–32 4 KatsunoM,YokotaH,YamamotoY,TeramotoA.Bilateraltraumatic abducens nerve palsy associated with skull base fracture—case report. Neurol Med Chir (Tokyo) 2007;47(7):307–309 Funding 5 Hollis GJ. Sixth cranial nerve palsy following closed head injury in None. a child. J Accid Emerg Med 1997;14(3):172–175 Indian Journal of Neurosurgery Vol. 4 No. 3/2015.
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